It is very common to sell cigarettes in a hinged-lid (HL) carton or pack made of cardboard or other such material. A HL pack is generally provided with a transparent outer cellophane wrapping. This wrapping is then removed by a consumer in order to gain access to the cigarettes or other smoking articles contained in the pack.
A HL pack is usually rectangular in shape and comprises a body portion and a lid portion having a hinged attachment to one another. The body comprises opposing front and back panels, two opposing side panels, and a bottom panel, while the lid comprises opposing front and back panels, two opposing side panels, and a top panel opposing the bottom panel of the body. The back panels of the lid and body are joined together by the hinged attachment. The side panels and front panel of the body abut corresponding side and front panels of the lid when the lid is closed. The binge line between the back panels is generally higher (nearer the top of the pack) than the line of abutment between the front panels, so the lines of abutment between the lid and body side panels slop diagonally downwards towards the front of the pack.
HL packs are generally provided with an inner frame which is glued to the inside of the body portion of the pack. The inner frame typically comprises a front panel and opposing side panels which extend past the line of abutment between the body and the lid. Consequently, if the lid does not mate exactly with the body of the pack, the inner frame prevents the product inside the pack from being exposed.
One known problem with existing HL packs is that the lid may not always stay completely shut, especially after the cellophane wrapping has been removed. Most frequently, the lid may sit slightly ajar of the pack, although in more extreme cases, the lid may flop open completely. This tendency is sometimes known as yawning. Such yawning can assist unwanted ingress/egress to/from the pack—e.g. moisture loss from the cigarette tobacco. If the lid becomes very loose, there is a risk that some of the contents may fall out when the pack is lifted. In addition, a pack with an improperly closed lid generally has a low quality appearance.
Yawning tends to become an increasing problem as cigarettes or other smoking articles are consumed from the pack. There are two main reasons for this. Firstly, movement of the lid may be opposed by frictional engagement with the inner frame. However, this frictional engagement is generally reduced by repeated opening and closing of the lid (to access products in the pack), for example as the cardboard of the pack becomes worn and/or bent. Secondly, a pack is normally designed such that there is a slight interference (usually less than 1 mm) between the product in the pack (when full) and the opening action of the lid. In other words, opening the lid of a full pack of cigarettes requires a slight, temporary compression of some of the cigarettes in the pack. However, after some of the cigarettes have been removed from the pack, this allows space for the remaining cigarettes to move at least partly towards the rear of the pack, thereby removing any interference between the cigarettes and the opening action of the lid.
U.S. Pat. No. 5,904,244 discloses a hinge-lid carton for cigarettes with a closure aid to help keep the pack shut. The closure aid involves inner side tabs that extend up from the side walls of the body of the pack to engage inner side tabs within the lid of the pack. Another known mechanism to address yawning is to provide outwardly facing lugs or ears on the inner frame where it extends above the body of the pack. These lugs frictionally engage the lid when it is closed, and thereby help to hold the lid in place to prevent yawning. An example of such ears can be seen in WO 96/09230. However, such lugs are not always effective, and they can sometimes lead to creasing of the inner frame (which may be formed of a less rigid material than the main body of the pack).